Absorbent articles such as disposable diapers, adult incontinent pads, sanitary napkins and the like come in many different sizes and shapes. Diapers and incontinent pads are generally garments worn by infants or incontinent persons that are drawn up between the legs and fastened about the waist of the wearer. Sanitary napkins are designed to receive and contain vaginal discharges, such as menses, and are typically held adjacent to the human body through the agency of a garment, such as an undergarment or a panty, or a specially designed belt.
Typically, absorbent articles comprise a liquid pervious material that faces the wearer's body, a liquid impervious material that faces the wearer's clothing, and an absorbent body or absorbent core that is sandwiched between the liquid pervious material and the liquid impervious material. In prior absorbent articles, a material comprising comminuted wood pulp, referred to as airfelt, was used in the absorbent core to serve the functions of acquiring, distributing, and storing liquids and other exudates deposited on the surface of the absorbent article. One of the disadvantages of using airfelt was that a thick layer of airfelt had to be used to obtain the needed capacity.
Recent attempts to improve the effectiveness of absorbent cores have included distributing particles of absorbent gelling material throughout or in portions of the absorbent core. Some of these improvements are described in U.S. Pat. No. 4,610,678 issued to Paul T. Weisman and Stephen A. Goldman on Sept. 9, 1986; U.S. Pat. No. 4,673,402 issued to Paul T. Weisman, Dawn I. Houghton, and Dale A. Gellert on Jun. 16, 1987; and European Patent Application EP-A-254,476 assigned to The Procter & Gamble Company, published Jan. 27, 1988, the disclosures of which are incorporated by reference herein. Another improvement to the effectiveness of absorbent cores is described in U.S. Pat. No. 4,781,711 issued on Nov. 1, 1988 to Dawn I. Houghton and Nicholas A. Ahr, the disclosure of which is also incorporated by reference herein. While the absorbent articles described in the above references work quite well, the search for improved absorbent articles that are capable of rapidly and efficiently absorbing increasingly greater quantities of exudates has continued.
The structure of the absorbent core ideally should be such that the absorbent article absorbs exudates immediately when they are discharged so that such exudates will not pool or otherwise remain on top of the core. The absorbent core ideally should also be constructed so exudates initially absorbed will be immediately transported to a place within the absorbent core where they can be stored. One problem with many of the prior absorbent articles that used absorbent gelling materials is that the absorbent gelling materials do not absorb liquid exudates as fast as they are deposited on the core. Slow absorbing absorbent gelling materials, thus, do little to increase the immediately available capacity of the core. Such absorbent gelling materials typically require several seconds or minutes to absorb fluids.
The absorbent core should also provide a system of distribution and storage for exudates that efficiently uses the entire capacity of the absorbent core. One problem that often arises in absorbent articles without such a system (particularly those absorbent articles that use the same layer or batt of material to serve the different functions of acquiring, distributing, and storing exudates) is that the storage capacity of the absorbent article is exhausted prematurely. This can occur in several different ways. In many absorbent articles, the saturation of the absorbent material in the region where exudates are initially deposited reduces the ability of the absorbent material to transport additional exudates to other parts of the core. This phenomenon can also lead to the undesirable pooling of exudates on top of the core discussed above.
In other absorbent articles the effectiveness of absorbent cores containing particles of absorbent gelling material can be adversely affected by a phenomenon called "gel blocking". The term "gel blocking" describes a situation that occurs when a particle of absorbent gelling material is wetted and the surface of the particle swells so as to inhibit liquid transmission into the interior of the absorbent core. Wetting of the interior of the absorbent core, therefore, takes place via a very slow diffusion process. In practical terms, this means that acquisition of liquid by the absorbent core is much slower than the discharge of the liquids to be absorbed, and leakage from the absorbent article may take place well before the particles of absorbent gelling material in the absorbent core are fully saturated or before the liquid can diffuse or wick past the "blocking" particles into the rest of the absorbent core.
Therefore, a need exists for an absorbent article that has an absorbent core that quickly acquires and distributes exudates throughout the absorbent core where they can be stored.
It is an object of the present invention to provide an absorbent core for an absorbent article which is especially efficient in acquiring, distributing, and storing exudates as they are deposited on the absorbent article.
In particular, it is an object of the present invention to provide an absorbent core that has a system in which the functions of acquiring and distributing exudates are handled by layers that are separate from the layers used for storing exudates. Ideally, such a system will allow exudates to be continuously acquired and distributed to storage layers by layers that are not subject to the prior problems of saturation and gel blocking.
These and other objects of the present invention will be more readily apparent when considered in reference to the following description and when taken in conjunction with the accompanying drawings.